Bayonetta

There are 9 Angelic Hymns in total, but you only need 7 of them to have the achievement (ie: obtain the six in the game and finish the hard mode for the seventh). Bring each one to Rodin, in Gates of Hell, to obtain new weapons. Here we go.

TROIS MARCHES MILITAIRES (single):
Chapter 1 -verse 4, Vigrid central station (Gaudì style). Impossible to miss, ‘cause you’ll obtain it after beating the first “Beloved” boss.

QUASI UNA FANTASIA (single):
Chapter 2 -verse 7, another LP you cannot miss, ‘cause is the prize for the battle with those 2 “Beloved”.

FANTAISIE IMPROMPTU (2 pieces):
Chapter 3 -verse 4, price for the first “Fairness” fight.
Chapter 3 -in Paradiso, garden of light (around verse 10), on a little island behind the heaven gate you came through. Walk on water, you cannot sink.

SONATE IN DK.448 (3 pieces):
Chapter 5 -verse 2, price for fighting “Grace & Glory”.
Chapter 5 -verse 5, price for beating the flock of Harmony (flying manta enemies).
Chapter 5, just after verse 9, while you’re walking on that rocky “snake spine” stairway leading up in the open (the one with all those wind spirits), at some point, on the left, there’s a round pool filled with water, with a column in the middle. The third piece is in an Umbra chest behind the column.

LES PATINEURS WALTZ OP.183 (3 pieces):
Chapter 6, in an Umbra chest just behind you at the beginning.
Chapter 6 -before verse 2, break some rocks on the left from the entrance, while you’re down in the water. Behind them you’ll find an Umbra chest with the second part of the disk.
Chapter 6 -verse 9, price for beating the “Joy” impostor. :-)

MESSIAH HWV.56 (3 pieces):
Chapter 9 -around verse 1. Go to the original exit of the Gaudì plaza. When you find the brick wall with the sun icon blocking your way, break it to discover an Umbra chest with the first part (watch it! There’s another wall with sun icon at the entrance of the plaza. In here you’ll find a portal, not the chest you need!).
Chapter 9 -verse 6, price for beating those two flying “Kinships”.
Chapter 9 -just after verse 8, instead of ascending with the light bridge (the one after the huge crashing ball), jump over the chasm. At the end of the walkway there’ll be another brick wall with the sun icon. Break it for the Umbran chest with the final part.

HALLELUJAH (single):
Beat 100 chapters at normal or higher difficulty for the Sa-Fung nunchucks. Chapter 1 for 100 times will do, but I think a boss chapter like the fourth or the seventh would be shorter.

JUPITER, THE BRINGER OF JOY (single):
Beat the game at “Non-Stop Climax” difficulty, and you’ll have Pillow Talk saber.

MARS, THE BRINGER OF WAR (single):
Beat “Hard Mode” for the Bazillions pistols.

To see which Angelic Hymns you got it press back button, go to files and Angelic Hymns.

You need every Angelic Hymn you can get through normal play, +1. There are a few extra, secret weapons you can unlock and you'll need one of these for the achievement.
Bazillions is unlocked by completing the game on Hard.
Sai-fung is unlocked by completing 100 chapters (Normal difficulty or above, and repeated chapters do count - just make sure you do it on the same save.)
Pillow Talk is unlocked by completing the game on Non-Stop Climax difficulty (but you would have already completed the game on hard by this point.)
Rodin is unlocked by defeating Rodin. This is CRAZY hard. First you need to earn 10 million halos total. Then you need to buy the Platinum Ticket for 999,999 halos. Then... you need to win. It is possible that you unlock this weapon before the others but I wouldn't recommend it!